A fuel injection apparatus is installed in a vehicle (e.g., an automobile). The fuel injection apparatus injects fuel into a cylinder of an internal combustion engine, such as a diesel engine.
In a previously known fuel injection apparatus, an injector is provided to directly inject high pressure fuel, which is supplied from a high pressure generating device (e.g., a fuel injection pump or a common rail), into the cylinder of the internal combustion engine.
One such an injector is a fuel injection valve that has a fuel injection nozzle and a solenoid valve, which are integrally assembled together. The fuel injection nozzle includes an injection hole and a needle. The needle axially reciprocates to open and close the injection hole. The solenoid valve controls opening and closing movement of the needle. This kind of injector is disclosed in, for instance, JP4363369B2 and JP2007-205263A.
FIGS. 12 and 13 illustrate a previous proposed injector of one such a type. As shown in FIGS. 12 and 13, the injector has a solenoid valve, which includes a valve 103, an armature 104, a spring 105 and a solenoid (also known as a solenoid actuator). The valve 103 opens and closes a valve hole 102 of a valve seat 101. The armature 104 is made of a magnetic metal material. The armature 104 drives the valve 103 toward the valve hole 102 in a valve-opening direction. The spring 105 urges the valve 103 in a valve-closing direction, which is opposite from the valve-opening direction. The solenoid includes a coil 106. When the coil 106 is energized, a magnetic attractive force, which magnetically attracts the armature 104 is generated from the solenoid.
The solenoid includes a coil device and a stator 109. The coil device includes the coil 106, a resin bobbin 107 and a resin mold 108. The stator 109 is made of a magnetic metal material and magnetically attracts the armature 104 upon the energization of the coil 106.
The armature 104 is slidably supported in a slide hole 112 of a valve body 111 made of a non-magnetic metal material. A housing 113, which is made of a non-magnetic metal material, is placed at an upper end portion of the stator 109. A connector 114, which is made of a synthetic resin material, is molded at an upper end portion of the housing 113.
The coil device of the solenoid further includes terminals 115, 116 besides the coil 106, the resin bobbin 107 and the resin mold 108.
Fuel drain passages 121-127 are formed in an inside of the injector, particularly in the solenoid valve to return fuel, which is leaked from the inside of the fuel injection nozzle, to a fuel tank.
In the injector, it is important to limit the leakage of the fuel, which is guided into the inside of the solenoid valve, to the outside. That is, it is important to limit the leakage of the fuel from the fuel drain passages 121-127 to the outside.
However, in the solenoid valve of the previously proposed injector, the resin bobbin 107 is molded from a thermoplastic resin material, and the resin mold 108 is molded from a thermoset resin material. Thus, the resin materials, which respectively have different coefficients of thermal expansion, are used to form the resin bobbin 107 and the resin mold 108, respectively.
Furthermore, in order to electrically insulate between the housing 113 and the terminals 115, dielectric bushes 118, 119 are received in a terminal receiving hole 117 of the housing 113.
The dielectric bushes 118, 119 are molded from a thermoplastic resin material. Therefore, a coefficient of thermal expansion of the dielectric bushes 118, 119 differs from the coefficient of thermal expansion of the housing 113 and the coefficient of thermal expansion of the terminals 115.
With the above construction, fuel leak passages 131, 132, which are located on the radially inner side of the resin bobbin 107, and a fuel leak passage 133, which is located on the radially outer side of the resin bobbin 107, are provided at a boundary surface between the resin bobbin 107 and the resin mold 108, a boundary surface between the resin bobbin 107 and the stator 109, a boundary surface between the resin mold 108 and the stator 109, a boundary surface between the resin mold 108 and the terminals 115 and a boundary surface between the dielectric bushes 118, 119 and the terminals 115.
In the previously proposed solenoid valve, in order to limit leakage of fuel from the fuel drain passage 122 to the outside through the fuel leak passages 131-133, two O-rings 141, 142 are placed in the terminal receiving hole 117.
In this way, the fuel leak from the inner passages to the outside can be limited.
However, in the solenoid valve installed in the previously proposed injector, the shape of the terminal receiving hole 117 and the outer shapes of the dielectric bushes 118, 119 become complicated due to the use of the two O-rings 141, 142. Furthermore, the size of the solenoid in the axial direction cannot be reduced. In addition, in the solenoid valve of the previously proposed injector, the two O-rings 141, 142 are required. Therefore, the number of the components and the number of the assembling steps are disadvantageously increased to cause an increase in the product costs.